1. Field of the Invention
This invention relates generally to heat exchangers and is concerned more particularly with a flexible tube-in-tube type of heat exchanger wound into a coil of desired size.
2. Discussion of the Prior Art
A tube-in-tube type of heat exchanger may comprise a coaxial pair of annularly spaced inner and outer tubular members through which respective first and second fluids flow. In one mode of operation, heat energy generally is transferred from the first fluid through the wall of the inner tubular member and to the second fluid which carries it away from the heat exchanger. Conversely, in another mode of operation, heat energy is carried to the heat exchanger by the second fluid and transferred through the wall of the inner tubular member to the first fluid flowing therein. Thus, in either mode of operation, heat energy is transferred through the wall of the inner tubular member which, accordingly, is made of good heat conductive material, such as copper, for example.
In a high pressure tube-in-tube type of heat exchanger, the inner tubular member may be replaced by a plurality of smaller diameter tubular members fed in parallel. As compared to a single inner tubular member made of the same material, the combined bundle of smaller diameter tubular members may provide an equivalent cross-sectional area for maintaining a similar rate of fluid flow, and an equivalent surface area for maintaining a similar rate of heat transfer. However, the multiple smaller diameter tubular members provide the additional advantage of operating more efficiently with considerably less wall thickness than the wall thickness required for the single inner tubular member in a high pressure heat exchanger.
Most of the tube-in-tube type heat exchangers of the prior art have outer tubular members made of rigid material. Furthermore, the inner tubular members generally are supported in radially spaced relationship with the wall surfaces of the outer tubular member to ensure that the second fluid in the outer tubular member flows along the entire outer surfaces of the inner tubular members. Consequently, the structural configurations of these prior art heat exchangers generally are fixed in design for fitting in spaces of predetermined size. As a result, if the space available for the heat exchanger is modified in size, the structural configuration of a prior art heat exchanger can be changed only with great difficulty; or a new heat exchanger of more suitable configuration may be required.
Therefore, it is advantageous and desirable to provide a tube-in-tube type heat exchanger having sufficient flexibility for winding it into a coil of desired size for fitting into the space available.